If you look very closely at Matt Damon's ear you'll notice something...
His rep stated that:
"Matt had a terrible spasm in his neck/back and he had to have acupuncture Those are acupuncture "needles' in his ear."
Sometimes after a treatment ear seeds or tiny needles are put into the ear with skin colored tape. This is done to help stimulate acupuncture points in the ear that correspond to different parts of the body. Ear seeds/needles can be helpful in sustaining the treatment effects.
I'm glad Matt is a fan of acupuncture!